Transcript Describe the Periodic Table

Probing the Periodic
Table
History of the Periodic Table
• Elements are the basic building blocks of
all things.
• Elements are made of atoms, They are
small, but they have mass too.
• The atomic mass of an element is the
weight of one atom of the element.
History of the Periodic Table
• In 1869, Dmitri Mendeleev listed all the
elements known at the time in order of
their atomic weight. He arranged the list
into a table of rows and columns.
• In Mendeleev’s day, there were 63 known
elements. Today, we know of almost 100
elements that can be found in nature.
Describe the Periodic Table
Describe the Periodic Table
• The periodic table is a chemistry
reference
• It arranges all the known elements
in an informative grid
Describe the Periodic Table
• Elements are arranged left to right
and top to bottom in order of
increasing atomic number
• This order usually coincides with
increasing atomic mass
Describe the Periodic Table
• The Table's pattern and arrangement
shows the arrangement of electrons in
the atom.
• Elements have different atomic numbers
- the number of protons or electrons
increases up the table as electrons fill the
shells (orbit levels).
Describe the Periodic Table
Elements have different atomic masses the number of protons plus neutrons
increases up the table.
• Rows - elements of each row have the
same number of orbit levels (shells).
• Columns - elements have the same
number of electrons in the outermost
energy level or shell (one to eight).
Describe the Periodic Table
• The different rows of elements are called
periods.
– The period number of an element signifies the
highest energy level an electron in that
element occupies
• The different columns of elements are
called groups or families
– Elements in the same family have similar
properties
Describe the Periodic Table
Describe How To Read The
Periodic Table
Describe how to read the
periodic table:
• Every table has:
Describe how to read the
periodic table:
Atomic Number
The number of protons in an atom
identifies the element.
The number of protons in an atom is
referred to as the atomic number of that
element.
Describe how to read the
periodic table:
Atomic Symbol:
The atomic symbol is one or two letters
chosen to represent an element ("H" for
"hydrogen," etc.).
These symbols are used every where in
the world
Usually, a symbol is the abbreviation of
the element or the abbreviated Latin
name of the element.
Describe how to read the
periodic table:
Atomic Mass:
The atomic mass is the average mass of
an element in atomic mass units ("amu").
Though individual atoms always have a
whole number of amu’s, the atomic mass
on the periodic table is shown as a
decimal number because it is an average
of all the isotopes of an element.